.flex {
  display: flex;
  position: relative;
}
.inline-flex {
  display: inline-flex;
  position: relative;
}

.flex,
.inline-flex {

  &.flex-nowrap { flex-wrap: nowrap; }
  &.flex-wrap { flex-wrap: wrap; }
  &.flex-wrap-re { flex-wrap: wrap-reverse; }

  &.direction-row { flex-direction: row } // （默认值）主轴为水平方向，起点在左端
  &.direction-row-re { flex-direction: row-reverse }
  &.direction-column { flex-direction: column }
  &.direction-column-re { flex-direction: column-reverse }

  &.content-start { justify-content: flex-start; }
  &.content-center { justify-content: center; } // 主轴居中
  &.content-end { justify-content: flex-end; }
  &.content-space-between { justify-content: space-between; } // 间隔相等，两端顶格
  &.content-space-around { justify-content: space-around; } // 间隔相等，两端顶格

  &.align-items-start { align-items: start; }
  &.align-items-center { align-items: center; } // 交叉轴居中
  &.align-items-end { align-items: flex-end; }

  .flex-1 { flex: 1; } // 自动占满
  .flex-2 { flex: 2; }
  .flex-3 { flex: 3; }
  .shrink-0 { flex-shrink: 0; } // 拒绝自动缩小

  .align-self-end { align-self: flex-end; }
}
